The present invention relates to a fluorescent display device for displaying characters and symbols by utilizing fluorescence and, more particularly, to a fluorescent display device having a light-emitting display section having light-emitting elements in a matrix form.
A conventional fluorescent character display tube is described in Japanese Patent Disclosure No. 53-141570 wherein grids of a predetermined number of characters and a plurality of phosphor dots in a matrix (e.g., 5.times.7 dots) are arranged so as to oppose the grids, and time-division pulses are sequentially applied to the grids to display characters and symbols.
However, in a fluorescent character display tube of this type, the number of dots is increased in accordance with a variety of display characters, and the number of lead wires connected to the fluorescent character display tube is increased in accordance with an increase in the number of characters to be displayed (i.e., grids). The wiring operation becomes complicated in accordance with the increases described above, and thus the number of drive elements for driving the grids and the phosphor dots is increased, resulting in high cost. In addition, since the grids are sequentially driven in response to the time-division pulses, the duty factor is decreased in accordance with an increase in the number of characters (i.e., grids), and a drive voltage required for the necessary luminance is raised. As a result, expensive elements having a high dielectric withstand voltage must be used. In addition to this disadvantage, drive elements are not often easily accessible.
In addition to the above-mentioned fluorescent display tube, other types of fluorescent display tubes have been proposed which perform graphic display, as described in Japanese Patent Publication No. 56-24993 and Japanese Patent Disclosure No. 57-99688. Each of these fluorescent display devices comprises a display unit obtained such that MOSFET switching elements, fluorescent screen electrodes connected to the MOSFET switching elements, a memory including capacitors, and a shift register for driving the switching elements are formed on a single semiconductor substrate.
The display device of the type described above can be effectively operated even if the number of lead wires connected to the fluorescent display tube is increased. However, the memory comprises a dynamic memory of capacitors, so the number of times of refreshing must be increased to perform high-luminance display. In other words, a high-frequency signal must be used. In particular, when the number of display elements is increased, a required number of times of refreshing cannot be performed, and so luminance is degraded, resulting in flickering on the phosphor screen.